The present invention relates to industrial process control or monitoring systems of the type used to control or monitor an industrial process. More specifically, the present invention relates to temperature transmitters which are used to sense a temperature of the industrial process.
Process variable transmitters are used to measure process parameters in a process control or monitoring system. Temperature transmitters typically include a sensor, an analog-to-digital converter for converting an output from the sensor into a digital format, a microprocessor for compensating the digitized output and an output circuit for transmitting the compensated output. Typically, this transmission is over a process control loop, such as a 4-20 mA current loop. One example parameter is temperature which can be sensed by measuring the resistance of an RTD (Resistive Temperature Device), also called a PRT (Platinum Resistance Thermometer) sensor, or a voltage output of a thermocouple sensor.
As the temperature sensor in the process variable transmitter ages, its accuracy may tend to degrade especially if the sensor experiences excessive temperatures above or below the standard temperature range of the sensor. This degradation may lead to a complete failure in which the sensor or the transmitter itself needs to be replaced. Further, the degradation may result in errors in the temperature readings. This may go unnoticed and lead to inaccuracies in the monitoring or control of the industrial process.